Method of controlling deposition of a continuous elongated element in building a tyre for vehicle wheels, process and apparatus for building a tyre for vehicle wheels

Abstract

A method of controlling deposition of a continuous elongated element in building a tire for vehicle wheels, includes: feeding an initial end of a continuous elongated element of elastomeric material through a slit bounded by a first roller and a second roller of a calender; retaining the continuous elongated element against a peripheral surface of the first roller; laying the initial end of the continuous elongated element against a deposition surface; rotating the calender around an oscillation axis that is substantially coincident with a contact generatrix between the first roller and the second roller; and dragging along the continuous elongated element together with the deposition surface.

Claims

1. An apparatus for building a tyre for vehicle wheels, comprising: a forming drum capable of rotating about an axis thereof; an extruder; a calender mounted on a frame and comprising a first roller and a second roller disposed close to each other at radially peripheral portions thereof and defining a slit, wherein the frame is movable relative to a supporting base of the frame around an oscillation axis, wherein said oscillation axis is parallel to rotation axes of the first and second rollers and substantially coincident with a contact generatrix between the first roller and the second roller; and an actuating device acting on the frame for moving the calender around the oscillation axis between a first position, at which the first roller is spaced apart from the forming drum, and a second position, at which the first roller is disposed close to said forming drum.

2. The apparatus as claimed in claim 1, wherein the calender comprises a motor operatively coupled to the second roller.

3. The apparatus as claimed in claim 1, comprising a friction mechanism operatively interposed between the first roller and the second roller.

4. The apparatus as claimed in claim 3, wherein said friction mechanism is movable between at least one engagement position, at which said friction mechanism drives the first roller in rotation, and a disengagement position, at which the first roller is an idle roller.

5. The apparatus as claimed in claim 1, wherein an outlet opening of the extruder is fixed relative to the supporting base.

6. The apparatus as claimed in claim 5, wherein the diameter of the second roller is between about 80 mm and about 250 mm.

7. The apparatus as claimed in claim 1, wherein the first roller has a diameter greater than a diameter of the second roller.

8. The apparatus as claimed in claim 7, wherein the diameter of the first roller is between about 90 mm and about 300 mm.

9. The apparatus as claimed in claim 1, wherein the actuating device comprises a pneumatic piston mounted between the frame and the supporting base.

10. The apparatus as claimed in claim 1, comprising an auxiliary wheel mounted on the supporting base and disposed close to the first roller.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) This description will be set out hereinafter with reference to the accompanying drawings, given by way of non-limiting example, in which:

(2) FIG. 1 diagrammatically shows a plant for building tyres for vehicle wheels;

(3) FIG. 2a is an elevation side view of an apparatus according to the invention belonging to the plant in FIG. 1, in a first operating configuration;

(4) FIG. 2b shows the apparatus in FIG. 2a in a second operating configuration;

(5) FIG. 3 is an elevation side view of the apparatus of the invention from a side opposite to that in FIGS. 2a and 2b, in the first operating configuration;

(6) FIG. 4 is a front view of the apparatus seen in FIGS. 2a, 2b and 3;

(7) FIG. 5 is a half-section view of a tyre for vehicle wheels obtained following a process in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

(8) With reference to the drawings, a plant for building tyres for vehicle wheels comprising at least one apparatus 2 for building a tyre for vehicle wheels according to the invention has been generally identified with reference numeral 1.

(9) Plant 1 is designed to manufacture tyres 3 essentially comprising a carcass structure 4 having at least one carcass ply 5. A layer of an airtight elastomeric material or liner 6 can be applied internally of the carcass ply/plies 5. Two annular anchoring structures 7 each comprising a so-called bead core 7a carrying an elastomeric filler 7b at a radially external position are in engagement with respective end flaps 5a of the carcass ply or plies 5. The annular anchoring structures are integrated in the vicinity of regions usually identified as beads 8, at which usually engagement between tyre 3 and a respective mounting rim occurs. A belt structure 9 comprising one or more belt layers 9a, 9b is circumferentially applied around the carcass ply/plies 5 and a tread band 10 is circumferentially superposed on the belt structure 9. So-called under-belt inserts 11 can be associated with the belt structure 9 and they are each located between the carcass ply/plies 5 and one of the axially opposite end edges of the belt structure 9. In addition or as an alternative to the under-belt inserts 11, annular inserts (not shown) of elastomeric material and/or comprising textile or metallic cords substantially parallel to the circumferential extension direction of the tyre (a zero-degree belt layer) or other reinforcing elements can be radially superposed at least on the axially opposite end edges of the belt layers 9a, 9b, and/or interposed between the same belt layers 9a, 9b at least at said end edges. Two sidewalls 12, each extending from the corresponding bead 8 to a corresponding side edge of the tread band 10, are applied to the carcass ply/plies 5 at laterally opposite positions.

(10) The aforesaid components of elastomeric material of tyre 3 are manufactured on one or more forming drums by moving said forming drums between different work stations at each of which suitable deposition units preferably apply basic semifinished products onto the forming drum or drums.

(11) In a preferred embodiment diagrammatically shown in FIG. 1 by way of example, plant 1 comprises a carcass-building line 13 at which one or more forming drums 14 are sequentially moved between different work stations designed to form a carcass sleeve on each forming drum 14, which carcass sleeve comprises the carcass ply/plies 5, liner 6, annular anchoring structures 7 and possibly at least part of the sidewalls 12. Simultaneously, in an outer-sleeve building line 15, one or more auxiliary forming drums 16 are sequentially moved between different work stations designed to form an outer sleeve on each auxiliary drum 16, which outer sleeve comprises at least the belt structure 9, tread band 10, and possibly at least part of the sidewalls 12.

(12) Plant 1 further comprises an assembling station 17 at which the outer sleeve is removed from the auxiliary drum 16 to be coupled to the carcass sleeve.

(13) Tyres 3 built by plant 1 are sequentially transferred to at least one vulcanisation unit, not shown.

(14) In accordance with the present invention, at least one of the components of elastomeric material of tyre 3, such as liner 6, fillers 7b and/or other parts of elastomeric material in beads 8, sidewalls 12, tread band 10 and/or others, is obtained by means of the above mentioned apparatus 2. One or more apparatuses 2 of this type can belong to the carcass-building line 13 and/or the outer-sleeve building line 15.

(15) This apparatus 2 comprises at least one feeding unit 18 to supply a continuous elongated element 19 of elastomeric material.

(16) In the embodiment illustrated in a non-limiting sense the feeding unit is an extruder 18 provided with a cylinder into which elastomeric material is introduced. The cylinder, heated to a controlled temperature, operatively houses a rotating screw by effect of which the elastomeric material is pushed along the cylinder towards an outlet opening or die 20 of extruder 18. Consequently, delivered through the outlet opening 20 is the continuous elongated element 19 of raw elastomeric material having a substantially circular cross-sectional profile. Alternatively, the conformation of the outlet opening 20 and, as a result, the cross-sectional profile of the continuous elongated element 19, can be of the ellipsoidal type.

(17) The continuous elongated element 19 coining from extruder 18 is guided to a calender 21 comprising a first roller 22 and a second roller 23 that can rotate around respective parallel rotation axes and are moved close to each other at their radially peripheral portions.

(18) The radially peripheral surface of the first roller 22 is of a substantially cylindrical conformation or in the form of a barrel, while the radially peripheral surface of the second roller 23 has a circumferential groove of suitable conformation (shown in FIG. 4). Thus a shaped slit 24 is defined between the mutually approached rollers 22, 23. The diameter D.sub.1 of the first roller 22 is included between about 90 mm and about 300 mm and the diameter D.sub.2 of the second roller 23 is included between about 80 mm and about 250 mm.

(19) The two rollers are preferably made of metal material and do not suffer deformation when the continuous elongated element 19 passes through slit 24, so as to give the desired section to element 19.

(20) The two rollers 22, 23 of the calender 21 are mounted on a first face 25a of a frame 25 in turn installed on a supporting base 26. Frame 25 has the shape of a plate and carries, pivotally mounted thereon, the pivot pins of the two rollers 22, 23 lying parallel like the respective rotation axes.

(21) A first gear wheel 27 is rotatably mounted on the first face 25a of frame 25 (FIG. 4) and the first roller 22 is coaxial with said first gear wheel 27 and is connected thereto through a friction mechanism 28 only diagrammatically shown in the form of a box-shaped body (not visible as it is radially internal relative to the gear wheel 27). The friction mechanism 28 is movable between an engagement position, at which the gear wheel 27 is integral with the first roller 22 and rotates together with the latter, and a disengagement position at which the first roller 22 is uncoupled from the first gear wheel 27 and is an idle roller. A second gear wheel 29 is rotatably mounted to the first face 25a of frame 25 and the second roller 23 is coaxial and integral with said second gear wheel 29 (FIG. 4). The second roller 23 too rotates together with said second gear wheel 29. A third gear wheel 30 is idly mounted on the first face 25a of frame 25 and is placed alongside the second gear wheel 29 on the opposite side relative to the first gear wheel 27 (FIGS. 2a, 2b and 4). A fourth gear wheel 31 is idly mounted on the first face 25a of frame 25 (FIGS. 2a, 2b and 4) and is fitted on a shaft of an electric motor 32 (FIGS. 3 and 4), preferably mounted on frame 25 too. The second gear wheel 29 and third gear wheel 30 are disposed between the first gear wheel 27 and fourth gear wheel 31. A toothed belt 33 (shown in FIGS. 2a, 2b and 3 but not in FIG. 4) is partly wrapped around each of the gear wheels 27, 29, 30, 31 so as to transmit the rotation motion generated by the electric motor 32 to the first gear wheel 27 and the second gear wheel 29 in opposite ways.

(22) Frame 25 is hinged on the supporting base 26 around an oscillation axis X-X which is coincident with a contact generatrix between the first roller 22 and second roller 23, which generatrix is located at the shaped slit 24. The supporting base 26 has a portion 26 adjacent to the second face 25b of frame 25 on the opposite side relative to the first roller 22 and the second roller 23.

(23) A pneumatic piston 34 (FIG. 3) has an end connected to frame 25 and an opposite end connected to the supporting base 26 and is spaced from the oscillation axis X-X. The pneumatic piston 34 is an actuating device and extension or shortening of same, suitably controlled, causes rotation of frame 25 around said oscillation axis X-X.

(24) The supporting base 26 is in turn installed on a body 35 integral with the extruder and can be moved relative to said body 35 in a direction parallel to the oscillation axis X-X along two preferably bar-shaped guides 36, carried by said body 35 and by means of a motor 37.

(25) Apparatus 2 further comprises an auxiliary wheel 38 carried by the supporting base 26 at a lower end thereof in the vicinity of the first roller 22. In greater detail, the auxiliary wheel 38 is idly hinged on the free end of a support 39 the opposite end of which is connected to an auxiliary pneumatic piston 40 mounted on said supporting base 26. The auxiliary wheel 38 is free to rotate around an axis parallel to the oscillation axis X-X and around the rotation axes of the first roller 22 and second roller 23.

(26) One of the forming drums 14 carried and rotated around its main axis by a suitable device 41, such as a robotized arm, is brought in face of calender 21.

(27) In accordance with the method and process of the present invention, the extruder is set in operation and produces the continuous elongated element 19 coining out of the outlet opening 20 and passing through the calender slit 24. During the whole working, the outlet opening 20 is fixed relative to the supporting base 26 and faces slit 24.

(28) In this first step, the first roller 22 is spaced apart from the deposition surface 14a, i.e. the radially external surface 14a of the forming drum 14 (FIG. 2a). In addition, the first roller 22 is coupled to the second one 23 and moved by motor 32 through the engaged friction 28, the first and second gear wheel 27, 29 and the toothed belt 33. The number of teeth of the first gear wheel 27 and the second gear wheel 29 and the diameters D.sub.1, D.sub.2 of the first roller 22 and second roller 23 are of such a nature that the peripheral speed V.sub.1 of the first roller 22 is lower than the peripheral speed V.sub.2 of the second roller 23. For example, the ratio of the peripheral speed V.sub.2 of the second roller 23 to the peripheral speed V.sub.1 of the first roller 22 is included between about 1.05 and about 1.25 and is preferably of about 1.16. Preferably, in this first step, the peripheral speed V.sub.1 of the first roller 22 is included between about 40 m/s and about 240 m/s and the peripheral speed V.sub.2 of the second roller 23 is included between about 50 m/s and about 250 ms/s.

(29) Due to this difference in the peripheral speed, the continuous elongated element 19 adheres to and is retained on the peripheral surface of the first roller 22. The initial end 19a of the continuous elongated element 19 moves together with said peripheral surface of the first roller 22 and covers an arc of a circumference. Meanwhile, by operating the pneumatic piston 34, frame 25 is rotated around the oscillation axis X-X so as to move the first roller 22 close to the forming drum 14 and make the initial end 19a of the continuous elongated element 19 rest against the forming drum 14 (FIG. 2b) when said initial end 19a has carried out together with the first roller 22, a rotation included between about 70 and about 110, preferably equal to about 90, calculated starting from slit 24.

(30) The continuous elongated element 19 adheres to the radially external surface 14a of the forming drum 14, which surface can be the surface of the forming drum 14 itself or the surface of one or more elements already laid down on the forming drum 14.

(31) After routing of said continuous elongated element 19 between rollers 22, 23 of the calender 21 has occurred, as well as adhesion of said element 19 to one of the rollers, rotation of calender 21 allows the first roller 22 carrying the initial end 19a of said continuous elongated element 19 to move close to the forming drum 14 and enables application of the initial end 19a to the surface 14a radially external to the forming drum 14 in a simple and quick manner and without running the risk that parts in motion of calender 21 may interfere with drum 14 while rotating and with extruder 18 and that drum 14 may interfere with extruder 18 (in particular the reduction gearing and the gear pump of the latter).

(32) Powered rotation of the forming drum 14 drags along the continuous elongation element 19 together with the radially external surface 14a of said drum, causing winding up of said element into coils for example disposed in side by side relationship and/or partly superposed, on the drum 14 itself. To this aim, the robotized arm 41 moves the forming drum 14 in front of calender 21 during deposition. If the radially peripheral surface of the first roller 22 is rounded or convex, drum 14 can also be slightly inclined to said first roller 22 for laying down continuous elongated elements 19 on uneven surfaces.

(33) During winding into coils, the auxiliary wheel 38 presses the continuous elongated element 19 against the forming drum 14 for consolidating and compacting the elastomeric material. The auxiliary pneumatic piston 40 is able to take up possible unevenness present on the surface radially external to the forming drum 14.

(34) In accordance with an embodiment of the invention (FIG. 2b), during winding into coils, the first roller 22 is maintained against the forming drum 14, the continuous elongated element 19 being interposed therebetween, and rotates in an idle manner, being driven by the drum 14 itself by friction. The peripheral speed of the forming drum 14 can be the same as the peripheral speed V.sub.2 of the second roller 23 or greater. The pneumatic piston 34 takes up possible unevenness present on the surface radially external to the forming drum.

(35) In accordance with an alternative embodiment of the invention, immediately after application of the initial end 19a of the continuous elongated element 19 against the forming drum 14, the first roller 22 is again moved away from the surface 14a radially external to the forming drum 14 causing rotation of frame 25 in the opposite way around the oscillation axis X-X by means of the pneumatic piston 34.

(36) The continuous elongated element 19 is compacted by the auxiliary wheel 38 alone, and the calender 21 works separated from the forming drum 14. Preferably, in addition, the first roller 22 is again coupled to the second roller 23 and the electric motor 32 through the friction mechanism 28 and rotates being driven by belt 33.

(37) In accordance with a preferred embodiment, the friction mechanism 28 has a plurality of operating positions in addition to the idle one, so that under normal working conditions the first roller 22 is rotated at the same peripheral speed V.sub.1 as the peripheral speed of drum 14 and at the peripheral speed V.sub.2 of the second roller or at the same peripheral speed V.sub.1 as the peripheral speed of drum 14 and greater than the peripheral speed V.sub.2 of the second roller 23.

(38) On moving from the position spaced apart from the forming drum 14 to the position adjacent to the latter and vice versa, the pneumatic piston 34 carries out a stroke included between about 10 mm and about 15 mm, which value can be also different from that stated above depending on the position of the pneumatic piston 34, and the first roller 22 carries out a stroke included between about 10 mm and about 30 mm.

(39) When deposition has been completed, the residual continuous elongated element 19 is removed from calender 21, which calender 21 together with frame 25 can be moved apart from the outlet opening 20 of extruder 18, through sliding along guides 36, to enable purging and servicing of the extruder 18 itself.